Synology DiskStation DS1621xs+

NAS for small and medium businesses / ServerNews

Synology DiskStation DS1621xs + is a small, high-capacity and fast network storage that combines a six-drive cage, a pair of M.2 NVMe, 1 / 10GbE ports and a PCIe expansion card slot. And the Intel Xeon D-1527 processor, 32 GB RAM and DSM OS allow you to use it far from only as a NAS

Synology DiskStation DS1621xs + is a professional device, because Intel Xeon D-1527 (4 cores / 8 threads, 2.2 / 2.7 GHz, 6 MB L3 cache, TDP 35 W), from 8 to 32 GB DDR4- 2133 ECC and three network ports, one of which has a speed of 10 Gb / s, you’d expect to see more in some rack solution. However, in this case, this is not the case: the DS1621xs + is a desktop NAS that successfully combines a capacious disk subsystem, not the largest dimensions and sufficiently quiet cooling, allowing you to use the storage in the office. However, let’s talk about everything in order.

Synology DiskStation DS1621xs +

Synology DiskStation DS1621xs +

The device has dimensions of 166 × 282 × 243 mm and weighs 5.3 kg. This is not so much, because most of the frontal area, and also the volume, is occupied by a disk cage for six SATA-3 drives. On the sides of it there is a built-in power supply and a place for a PCIe 3.0 x8 expansion card, where you can install another network adapter (among the compatible ones there are also 4 × 10GbE), if there are not enough standard ones: one 10GbE and two 1GbE (with support for aggregation).

Inside the case, on the left side of the drive cage, there are two M.2 2280 slots for installing caching NVMe SSDs. The system is cooled by two 92 mm fans on the rear wall. They can be easily replaced without disassembling the entire case, as they are attached to a removable frame. The RAM is no less easy to change: there is a hatch on the bottom of the device, behind which two SO-DIMM slots are hidden. At the bottom there is a console port covered with a dense rubber plug.

Disc trays are universal. You don’t need anything at all to install a 3.5 ”HDD, but you will have to use screws to mount 2.5” drives. The trays, by the way, are plastic, but they don’t seem fragile. Each of them has a small lock on the bottom to lock the tray in the basket. The NAS naturally supports hot swap drives. And to increase the storage capacity, you can connect two external DX517 modules for five 2.5 “/ 3.5” SATA-3 disks each, for a total of 16 drives. The modules are connected via two eSATA ports located on the rear panel. There are also two USB 3.0 ports, and one more is located on the front panel.

On the front are all the main indicators: system status, error notifications, activity of all three network interfaces and drives (each tray has a light guide). The power button is combined with a power indicator. All indicators are quite bright by default, but in the settings you can choose one of three brightness levels or even turn off all the “illumination” at once. Network ports have their own activity indicators that cannot be disabled, but they do not interfere.

Synology DiskStation DS1621xs + Specifications
Storage devices 6 × 3.5 / 2.5 “SATA II / III HDD / SSD; 2 × M.2 2280 NVMe
2 × DAS DX517 (5 × 3.5 / 2.5 “SATA II / III HDD or SSD)
File system internal hard drives: EXT4, Btrfs
external media: EXT3, EXT4, Btrfs, NTFS, FAT, HFS +, exFAT
RAID SHR F1, Basic, JBOD, RAID 0, 1, 5, 6, 10
CPU Intel Xeon D-1527 (4/8, 2.2 / 2.7 GHz, 6 MB, TDP 35 W)
RAM 8GB DDR4 ECC UDIMM (expandable to 2x16GB)
Network interfaces 1 × 10GbE RJ-45;
2 × 1GbE RJ-45
Additional interfaces 3 × USB 3.0;
1 × PCI-E 3.0 x8 HHHL;
2 × eSATA (DAS)
Protocols CIFS, AFP, NFS, FTP, WebDAV, CalDAV, iSCSI, HTTP (S), rsync; VPN (PPTP, PPPoE, OpenVPN, L2TP / IPSec); IPv6; Telnet, SSH, SNMP
Clients Windows 7 and later, Mac OS X 10.10 and later;
iPhone OS, Android OS, Windows Mobile, Symbian OS
Cooling system 2 × 92 × 92 mm fans; noise level <25.2 dBA
Food PSU: AC 100-240 V, 50-60 Hz 250 W
Power consumption, W in access mode: 62.85
hibernation: 34.26
Working conditions 0-40 ° C; 5–95% RH
Dimensions, mm 166 × 282 × 243
Weight, kg 5.3 (without HDD)
Warranty, month 60
Estimated price, rub. 160,000

We’ve already come across Synology storage solutions aimed at small and medium businesses, with the DiskStation DS1618 + and RackStation RS1619xs + as examples. And here’s a coincidence – both of these devices are relatives of today’s test subject, not only in positioning. With the first, it has the same form factor, and with the second, it shares the hardware base. But the DS1621xs + has a clear advantage in the form of a 10GbE port. Let’s see what it gives, because we got an excellent addition to it – two proprietary SSD Synology SAT5200 with a capacity of 960 GB and 1.92 TB. These corporate drives are designed to work around the clock as part of NAS and enterprise storage systems. They were accompanied by two Seagate Exos X14 hard drives with a capacity of 14 TB (ST14000NM0018).

The test bench configuration is as follows: Intel Core i7-7700K, 32 GB RAM, NVMe SSD GOODRAM IRDM Ultimate, 1GbE Intel I219-V adapter (for accessing the web interface), 10GbE Intel X540-T2 adapter (for data exchange), Windows 10 Pro 2004. On 10GbE interfaces, 9k Jumbo frames were enabled on both sides. The HDD and SSD were combined into RAID 1 arrays. First, separately, and then using the SSD array to cache the HDD array, including sequential operations. In all cases, one Btrfs volume with one SMB share was created on the arrays. Well, the NAS itself was equipped with 8 GB of RAM, which is enough in our case.

The most difficult scenario, not too typical for a shared storage, however, is one-time read / write of a large amount of data. It shows the “true nature” of drives, that is, their speed characteristics. But even in this case, the presence of an SSD cache “pulls up” the overall performance well. And not only in terms of speed, but also in terms of IOPS. With repeated calls, caching is clearly visible. With small volumes, what gets into the RAM cache is enough – the speed and IOPS even for HDDs increase dramatically. It is thanks to him that in many cases it will be possible to simply run into a limitation on the part of the network connection.

However, the RAM is not rubber, and even without working additional applications, the system gives for the cache no more than seven gigabytes of RAM out of eight available in our configuration. Exceeding the amount of RAM drastically decreases the performance of random read operations. And if for SSD it falls by only two times, then for HDD it is almost an order of magnitude. The best option in this case is to use an SSD for caching, even if it is small relative to the rest of the storage capacity. This will hide the nature of the HDD from users, and the costs for such an “accelerator” will not be too high.

The company recommends using the Synology SSD as it provides a comprehensive, pre-tested and optimized solution from a single vendor. The list of compatible drives can be found on the official website, but as the NAS model is new, it will be updated more. There are no complaints directly about Synology drives, but there is one small caveat – when working intensively on random operations, SSDs are expected to heat up. In this case, up to +40 ° C, according to the DSM readings. And when any of the drives reaches this temperature, the fans automatically start to increase their speed.

Three profiles are available in the settings: quiet mode, cooling mode and maximum speed mode. All tests were carried out in the first mode, which is called quiet for a reason – the noise of the fans in it is blocked by the crackling of hard drives. Moreover, when using SSD caching, the NAS constantly moves data back and forth, so that HDDs are heard much more noticeably and more often, and the load on the SSD is slightly higher. So the NAS occasionally gets noisier for a few seconds. In an office environment on a working day it is unlikely to be noticeable, but at a “remote location” it can be a little disturbing.

However, DiskStation DS1621xs + still belongs to office solutions aimed at small and medium businesses. A faster processor than previous models in the series and a network connection naturally allows you to accelerate work with large amounts of data. This can be an increased number of users simultaneously working with shared NAS resources, and more heavy workloads such as processing massive media files, rendering, or providing storage for virtual machines (VMs).

But the capabilities of the device are determined not only and not so much by its “hardware”. It’s not about the number of disks, processors and 10GbE connection. The point is the set of capabilities that DSM OS provides. In the official repository of the manufacturer alone, there are dozens of applications and services that will greatly simplify the life of a business, taking on many typical office tasks and eliminating the need to buy a separate server or cloud capacity for them.

Active Backup for Business

Active Backup for Business

However, the most frequent and highly relevant task against the background of the sharply increased number of cyber threats amid the pandemic is still backup / recovery. Synology has several powerful and, importantly, free applications in its arsenal: Active Backup for Office 365 and G Suite for the cloud platforms of the same name, Cloud Sync for synchronizing files between NAS and two dozen different cloud storages, Glacier Backup for cold backing up data to AWS Glacier, HyperBackup for overall backup management (plans, replication, rotation, etc.), and Active Backup for Business.

The main – and very powerful – tool here is Active Backup for Business. It allows you to consolidate all your backup, recovery, and backup management and protection tasks. We already got acquainted with the main features of this solution last year. Since then, as promised, it has full support for Hyper-V. That is, now you can make automatic backup of virtual machines: save and restore snapshots, view and extract their contents, transfer VMs from host to host and from one hypervisor to another.

As before, all data has deduplication and flexible scheduling of old snapshots. VSS support has not gone anywhere, as well as the ability to run a script in a VM before and after backup to maintain data consistency. As in the case of VMWare, working with Hyper-V does not require the installation of agents – all interaction with the host takes place through WinRM, which is available by default in modern Windows Server and Microsoft Hyper-V Server. To get started requires only the server address and the login / password of the administrative account.

After connecting to Active Backup for Business, you will see a list of all virtual machines in the hypervisor. For each of them, in just a few clicks, you can set a schedule for creating and deleting backups. But the beauty of this solution is not at all in this, but in the flexible options for restoring damaged VMs. In the simplest case, rolling back to the selected state from the available copies is the transfer of the saved disk image back to the hypervisor. But there are also two alternatives.

The first is the so-called instant recovery. In this case, nothing is copied anywhere. Instead, a new LUN is automatically expanded from the backup and connected to the hypervisor, on the basis of which a new VM is formed with the same parameters as the original one. The presence of 10GbE-connection and SSD-caching allows you to do this trick with several machines at once – the performance of the disk subsystem and the NAS network will be enough for most workloads typical for small and medium-sized businesses.

The second option will come in handy already in a really emergency situation, when the server with the main hypervisor has failed or is unavailable. In this case, the VM from the copy can be deployed directly to the NAS using Virtual Machine Manager (VMM). The obvious limitation of this method is the CPU and RAM resources of the NAS itself. Well, for some imported VMs, you may need to change some settings.

VMM integrates Open vSwitch, QEMU with OVMF and other components, providing a convenient web interface for VM management. There are a number of useful features here. For example, built-in KVM access directly from the browser, for which you can generate a link for a remote connection. And there is also its own system for creating machine snapshots, managing VMM clusters on several storage systems / NAS, guest add-ons for VMs with Windows / Linux and, finally, the ability to deploy a full virtual copy of DSM. All this is available for free, and if you need more features, there is a VMM Pro license.


Synology DiskStation DS1621xs + is a very successful model in several ways. Among the current models of Synology, there are only two options for desktop NAS with built-in 10GbE ports: the hero of this review and 8-disk storage DS1817 on a radically different hardware platform. But the latter does not have PCIe or M.2 slots, so for the SSD cache you still have to “lose” a couple of places in the disk cage. Of the 6-disk models, the closest relative – DS1621 + – has a similar CPU in characteristics, support for a pair of M.2 SSDs and a PCIe slot, but lacks 10GbE ports.

DiskStation DS1621xs + has a free PCIe slot, an on-board 10GbE controller, and two M.2 ports that allow you to completely fill the basket with hard drives, getting both high capacity (96 TB if you take 16 TB drives) and good performance thanks to SSD caching. We, however, failed to test this scenario with NVMe disks, but it turned out well with SATA SSDs. Combined with the broad capabilities of DSM and a good chassis design, this adds up to a very attractive SMB NAS. But it also has a corresponding price – 160 thousand rubles for a configuration with 8 GB of RAM and without drives.